I sanded the top with the following grits of sandpaper: 100, then 150, then 220. I tried to fill the 2 marks I put in the top long time ago with sawdust and glue. The marks are still visible, but they look a bit better. After all the sanding, I "raised the grain". I did this by wiping the top with a damp paper towel. The dampness will make any small sanding scratches swell, then once dry I sanded again with 220 grit to end up with a nice smooth finish. Then I sealed the top by brushing on a thin coat of shellac.
Mahogany is a porous wood, so in order to get a smooth finish these pores have to be filled. I purchased some Timbermate filler from Stewart MacDonald. I got rosewood coloured filler, which is a bit darker then the mahogany, which will make the grain show more when its finished.
When I applied the filler to the sides, I did manage to get a little on the edge of the top. Since I sealed the top with shellac, all I had to do was wipe the filler off the top with a damp paper towel. This stuff sure is easy to work with and clean up!
Once all my sanding was done, I sealed the sides and back with shellac. The pic below shows the back with a single brushed on coat of shellac. The figure in the wood shows up nicely, and you can actually see a couple of flames in the back. Just imagine how it will look with a thicker, shiny coat of shellac?!